This enables us to have `GeoExt.version` and related properties from `GeoExt.Version` print sane values.

This was introduced in #201, see there for discussion. Since `MapPanelItem` might be the only class required by the autoloading mechanism, we need to ensure that `GeoExt.Version` is loaded.

I am 100% open to a more automatic and non verbose way of always having `GeoExt.Version` in the build (or being fetched lazily). PR more than welcome :wink: